A pulse wave, which is a time-dependent vascular conduction wave generated on the basis of changes in intra-arterial pressure in a living body, includes a lot of information relating to vascular dynamics ranging from a center (heart) to a periphery. Therefore, by understanding the feature of the waveform of the pulse wave of a test subject (living body), it is possible to diagnose how the heart of the test subject pumps, the behavior of a blood vessel, the state of a vascular wall, and the like, for example, and the feature of the pulse wave is used for the diagnosis of a heart disease and a peripheral arterial disease. For example, there has been known a technique in which the pulse wave of a test subject is acquired and subjected to second order differential and the vascular age of the test subject is estimated from an acquired acceleration pulse wave.
In addition, in PTL 1 described below, there has been disclosed a technique where, in a pulse wave data analysis system in which a pulse wave p-p interval is extracted from the pulse wave data of a test subject, a notch portion included in the pulse wave data is appropriately removed and a peak and a bottom are correctly detected. In this technique, first, from pulse wave data obtained by continuously measuring a pulse wave during a predetermined time, a bottom value and a peak value are sequentially detected along a temporal axis, and a bottom value and a peak value, adjacent to each other on the temporal axis, are regarded as a pair. In addition, a bottom-to-peak amplitude value, which is a difference between the bottom value and the peak value of each pair, is obtained. Next, as for the obtained bottom-to-peak amplitude value, a first amplitude value and a second amplitude value, which occur in succession on the temporal axis, are compared with each other, and when the relative value of the second amplitude value with respect to the first amplitude value is smaller than a predetermined threshold value, a bottom value and a peak value relating to the second amplitude value are temporarily deleted. In addition, furthermore, a third amplitude value existing posterior to the second amplitude value is compared with the second amplitude value, and when a relative value between the two is smaller than a predetermined threshold value, the bottom value and the peak value relating to the second amplitude value are regarded as noises and finally deleted. According to this technique, even if a respiratory amplitude fluctuation or an amplitude or the like derived from a body motion or the like exists in a pulse wave waveform, it is possible to adequately remove only a noise without deleting an intrinsic bottom value and an intrinsic peak value of the pulse wave.
PTL 1: Japanese Unexamined Patent Application Publication No. 2008-253579